Curvature retaining device for plate-shaped workpiece, curvature retaining method for plate-shaped workpiece, and curvature forming method for plate-shaped workpiece

A curvature retaining device for a plate-shaped workpiece curving and retaining the plate-shaped workpiece in an elastic deformation range thereof, the curvature retaining device comprising:

• two support points configured to abut against two separate points of one surface of the plate-shaped workpiece as seen from a direction orthogonal to a curved cross section of the plate-shaped workpiece;
• two pressing points configured to abut against positions of the other surface of the plate-shaped workpiece between the support points as seen from the direction orthogonal to the curved cross section of the plate-shaped workpiece;
• forward/backward drive means for moving at least either the two support points or the two pressing points forward and backward in a thickness direction of the plate-shaped workpiece;
• load detection means for detecting a load added to the two pressing points;
• and
• control means into which load data from the load detection means is input, the control means driving the forward/backward drive means such that a predetermined load is added,
• wherein the control means performs control such that projection of a shot is stopped at a point of time when a decrease in the load data input from the load detection means is stopped, or at a point of time when the load data reaches a predetermined load value in a case where peen forming is performed through the projection of the shot while the plate-shaped workpiece is curved,
• wherein the two support points abut against the one surface of the plate-shaped workpiece at a first distance therebetween, and the two pressing points abut against the other surface of the plate-shaped workpiece at a second distance therebetween shorter than the first distance as seen from the direction orthogonal to the curved cross section of the plate-shaped workpiece,
• wherein a middle point of the first distance and a middle point of the second distance match with each other, and
• wherein at least either of the two support points or either of the two pressing points are configured to be moved independently in a plane direction of a surface, the surface being perpendicular to the thickness direction, of the plate-shaped workpiece.